If you saw a " small black line " on someone poking out from top what is it?

maybe a weird memory , a while back i saw this girl i knew at the gym , she's not a regular member so don't see her there that often but it was so weird as she was walking by me ( i was sitting on a machine) to leave and go into change room. i though that i saw something weird , like there was this small black line poking out ( maybe an inch) and barely visible from her top and her side rib area. and then she like acted super weird when i noticed her walk by.

i could never figure out what it was and aren't really any pictures of her that show that area clearly and when i see her inperson at her job she's never wearing tops that would show it.

one theory was that it was part of a tattoo , perhaps the stem /bottom part of a rose or flower tattoo and rest was hidden under her top. but have never seen her with one there and she's never even talked about tattoo's although around 2023 she did get a small tattoo on her ankle , i've seen it before its definitely real

and 2 of her girlfriend's who she was living with around that time do for sure have tattoo's , both in same area ( side ) but one is a quote and other a design , neither a flower. so maybe she got one too but just never really likes to reveal it to anyone , so she has 1 for sure but weird if she had a second one that she kept to herself or just doesn't want me to see it for some reason?

only other theory i had was that it was part of her top that had for some reason fabric ripped or something and it looked like a line

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to explain further she was going to school for nursing so perhaps her reputation wasn't one who had a tattoo , i'm not sure but feel like its still pretty common for younger nurses to have one these days
If you saw a " small black line " on someone poking out from top what is it?
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